Electrophotographic multicolor copy process employing solubilizable dyes

ABSTRACT

An electrophotographic process and materials for the production of multicolor copies of a multicolor original in which an electrostatic charge is applied to a receptor sheet having a face portion subdivided into photoconductive segments containing sensitizing components in interspersed segments which cover different portions of the visible light spectrum and in which each such segment contains a solubilizable dye color corresponding to the color of the spectrum other than that to which the segment is sensitized and in which the exposed receptor is developed with a toner in which the dye component is soluble in response to toner activation for transfer of dye color from the developed receptor to copy sheets brought into surface contact therewith.

United States Patent Inventors App]. No.

Filed Patented Assignee Frederick O. Bach Villa Park;

Leo N. Chapin, Des Plaines; Robert Freed, Lincolnwood; Thomas J.Cernoch, Chicago, all of 111.

June 25, 1969 Dec. 28, 1971 A. B. Dick Company Niles, 111.

ELECTROPHOTOGRAPHIC MULTICOLOR COPY PROCESS EMPLOYING SOLUBILIZABLE DYES10 Claims, 6 Drawing Figs.

US. Cl 96/l.2, 117/175, 252/62.1, 96/1 7 Int. Cl ..G03g 13/00 V G03g9/00 Field of Search 96/1 .2, 1.5,

[56] References Cited UNITED STATES PATENTS 3,549,359 12/1970 Honjo eta1. 96/1.2 2,962,374 11/1960 Dessauer 96/1 3,212,887 10/1965 Miller etal. 96/1 3,329,590 7/1967 Renfrew 204/18 3,458,310 7/1969 Arneth et a196/1.2

Primary ExaminerGeorge F. Lesmes Assistant Examiner-M. B. WittenbergAttorneyMcDougall, Hersh, Scott & Ladd than that to which the segment issensitized and in which the exposed receptor is developed with a tonerin which the dye component is soluble in response to toner activationfor transfer of dye color from the developed receptor to copy sheetsbrought into surface contact therewith.

ELECTROPHOTOGRAPHIC MULTICOLOR COPY PROCESS EMPLOYING SOLUBILIZABLE DYESThis invention relates to an electrophoto'graphic process, materials andelements for the production of true color copies from multicolororiginals with but a single exposure to light.

It is an object of this invention to provide a process for producingtrue color copies of multicolor originals by use of anelectrophotographic technique which requires but a single exposure tolight; which makes use of a single-receptor sheet from which one or anumber of multicolor copies can be produced; in which multicolor copy isproduced by transfer from the receptor sheet to copy sheets for truecolor reproductions, and it is a related object to provide a compositionand elements for use in the practice of the same.

These and other objects and advantages of this invention willhereinafter appear for purposes of illustration, but not of limitation,an embodiment of the invention is illustrated in the accompanyingdrawings in which FIG. 1 is a top plan view of a portion of a receptorembodying the coatings applied in accordance with a preferred practiceof this invention;

FIG. 2 is an enlarged sectional view through a portion of the receptorsheet shown in FIG. 1;

FIG. 3 is a schematic sectional view similar to that of FIG. 2,illustrating the conditions existing in response to exposure to amulticolor original;

FIG. 4 is a schematic sectional view of the exposed receptor of FIG. 3after treatment with a developer composition; FIG. 5 is a schematicdiagram showing the transfer of the multicolor image from the receptorto a copy sheet; and

FIG. 6 is a top plan view of the multicolor copy produced from theexposed receptor of FIG. 5.

Briefly described, the concepts of this invention are practiced with areceptor provided with a number of photoconductive coatings each ofwhich is formulated to contain I) an organic insulating binder, such asan organosilicon resin, a butadiene-styrene copolymer resin, a modifiedalkyd resin and the like; (2) a photoconductor such as photoconductivezinc oxide or other photoconductive material such as described in theMiddleton et al. US. Pat. No. 3,l2l,006; (3) a sensitizing component,such as a sensitizing wavelength within the photo conductor to light ofa selected wavelength within the visible light spectrum while reflectingwavelengths outside said range, with each coating containing asensitizing ingredient which sensitizes the photoconductive coating to adifferent portion of the visible light range, whereby the total of thecoating provides sensitivity which covers the entire visible lightrange, and (4) a soluble dye component in each coating having a colortransfer value corresponding to the subtractive color for which theparticular coating is sensitized, as represented by a color produced bythe combination of ranges of light reflected by the sensitizedphotoconductor of the particular coating composition and in which theconcepts of this invention include the use of a developer which isformulated with a component, normally identified as a toner, whichcomprises a solid material in finely divided form which, in response toactivation as by heat, solvent, vapors or the like, functions as asolvent for the soluble dye component (4) of the photoconductive coatingto effect transfer of the dye color from the portions of the coatingimmediately underlying the activated solvent for transfer to copy sheetspressed into surface contact with the receptor to produce true colorcopies of multicolor originals in response to a single exposure.

By way of illustration, the visible spectrum may be subdivided intocontiguous segments, preferably three or more segments, such assubdivision of the visible light spectrum, assumed to be included withinthe range of 400-700 nm. into segments of about 400-500, 500-600 and600-700 nm. The sensitizng component for one coating would then beselected to sensitize the photoconductor to light of within the range of400-500 nm. (blue sensitivity) and to reflect light within the range of500-700 nm. This particular effect can be achieved by the use of adyestuff corresponding to the yellow layer in the well knownphotographic color processes based upon the subtractive tripack, such asAuramine 0 (Cl. 4!,000 The soluble dye component formulated into thedescribed coating composition is selected of a dyestuff having a yellowcolor or a color which represents the combination of the reflected lightrange of 500-700 nm.

Another or second coating is formulated with a sensitizing componenteffective to sensitize the photoconductor in the light range of 500-600nm. (green sensitivity), while reflecting light within the range of400-500 nm. and 600-700 nm. This can be achieved by the use of a magentacoating, when reference is made to the subtractive tripack system, suchas by formulating the coating composition to contain acridine red (C.I.45,000 The soluble dye component formulated into the described coatingwould be selected of a dyestuff having preferably a blue-red colorcorresponding to the combination of the reflected light within the rangeof 400-500 and 600-700 nm.

The third coating would be formulated to contain a sensitizing componentwhich sensitizes the photoconductor to absorbed light within the rangeof 600-700 nm. (red sensitivity), while reflecting light within therange of 400-600 nm. This can be achieved by a cyan coat, such as withPatent Blue (CI. 42045). The soluble dye component in the third coatingwould be selected of a dyestuff giving a blue-green color correspondingto the range of reflected light or the combination of colors within therange of 400-600 nm.

When based upon the amount of photoconductive zinc oxide, the describedcoating compositions can be formulated to contain the resinous binder inan amount within the range of 10-40 parts by weight of resinous binderper parts by weight of zinc oxide, and preferably in an amount withinthe range of 15-30 parts by weight of resinous binder per I00 parts byweight of zinc oxide. The sensitizing component or dyestuff isformulated in the coating composition in an amount within the range of0.001 to 5.0 part by weight per 100 parts by weight zinc oxide andpreferably within the range of 0.01 to 2.5 part by weight per 100 partsby weight of zinc oxide, the amount depending somewhat upon thesensitizing dye, such as 0.13 percent by weight of magenta color, as inthe form of acridine red having a spectral response in the range of495-620 A., 0.06 percent of the cyan color, as represented by PatentBlue having a spectral response in the range of 600-700 A., and 1.2percent by weight of the yellow color as represented by Auramine 0having a spectral response within the range of 405-500 A. It will beunderstood that, except for cost, more than 5.0 parts by weight ofsensitizer per 100 parts by weight zinc oxide can be used. The solubledye component can be formulated into each coating in an amount withinthe range of 05-200 parts by weight per 100 parts by weight of zincoxide and preferably in an amount within the range of l-5 parts byweight per I00 parts by weight of zinc oxide. The foregoing amounts ofsensitizer and soluble dye components to the percent by weight of thephotoconductive coatings formulated of photoconductive zinc oxide or aphotoconductor other than zinc oxide, but in which the percentage isadjusted by the weight ratio of zinc oxide to said other photoconductive material in the coating.

The soluble dye component is preferably formulated in the respectivecoating compositions as a dispersed dye but it will be understood thatthe soluble dye component can be incorporated in other states.

The coatings are produced from compositions containing the describedcomponents in combination with a diluent which is a solvent for theresinous binder and application may be made to the substrate in coatingweights, when formulated of a zinc oxide photoconductor, within therange of 8-40 pounds per 3,000 square feet of surface area, andpreferably within the range of 15-30 pounds per 3,000 square feet ofsurface area.

The separate coating compositions are applied or other wise imprinted onthe surface of the substrate in various patterns. The essentialrequirement is that the face of the coated substrate define a finalpattern of separate, small light responsive areas of each coatinginterspersed one with another substantially uniformly over the surfaceof the substrate in closely spaced relation.

This can be accomplished by application of the separate coatingcompositions in a pattern of dots, circles, beads, spheres, squares,lines or the like configurations. Since it is not essential that theseparate light responsive areas be arranged coplanar, it is preferred toapply the coating compositions either in the form of lines whichcrisscross one another over the surface of the substrate or morepreferably to apply one coating composition as a continuous coating overthe surface of the substrate and to apply the remaining coatings aslines which crisscross over the underlying base coat as islands or dotsof various configuration which overlie the base coat. Thus the receptorsheet will be formed of a substrate having portions coated with only onelayer of the first coating, other portions with two layers formed of thefirst and second coats and first and third coats; and still otherportions formed of three layers of the first, second and third coating,etc.

Having described the basic concepts of the invention from the standpointof compositions and construction of the elements employed, illustrationwill now be made by way of examples which represent the practice of theinvention and in the utilization thereof in carrying out the new andnovel process for multicolor reproduction of multicolor originals by theelectrophotographic technique. The description will hereinafter be madewith respect to a system of compositions based upon the subtractivetripack but it will be understood that the visible light spectrum can beotherwise divided for the selection of component identified as thesensitizing component and corresponding soluble dye component embodiedin each of the separate coating formulations.

EXAMPLE 1 Magenta coating composition: (green sensitive):

100 grams photoconductive zinc oxide (Photox 80New Jersey Zinc Company)25 grams modified alkyd resin (DeSoto E-l04l3A DeSoto Chemical Coatings,Inc.

0.13 gram sensitizing dyeAcridine Red-Cl. 45,000 (Allied Chemical Corp.)

1.5 grams dispersed dye-spirit soluble Fast Red 33 60 ml. tolueneEXAMPLE 2 Yellow coating composition (blue sensitive):

100 grams photoconductive zinc oxide (Photox 80) 25 grams modified alkydresin (DeSoto E- 104l3A) 0.05 gram sensitizing dye-Auramine O--C.l.41,000 (Allied Chemical Corp.)

[.5 grams dispersed dyeCalcofast Spirit Yellow TG (American CyanmidCompany) 60 ml. solvent-toluene EXAMPLE 3 Cyan coating composition (redsensitive): 100 grams photoconductive zinc oxide (Photox 80) 25 gramsmodified alkyd resin (DeSoto E- 104-13A) 0.05 gram sensitizingdye-Patent Blue-Cl. 42,045 (Allied Chemical Corp.) 1.5 grams disperseddyespirit soluble Fast Blue 6G (Allied Chemical Corp.) 60 ml.solvent-toluene ln each of the examples, the resinous binder, zinc oxideand solvent are first blended together by mixing for about minutes. Thesensitizing dye, in solution in methanol, is added and blended by mixingfor about 1 minute. The dispersed dye is finally added and blended withmixing for about 1 to 2 minutes.

The first coating 20, which may be the magenta coat of example isapplied either by a roller coater, by a metering rod,

or by hand draw-down with a wire wound rod, onto Weyerhauser Base Apaper it) in a coating weight of about 20 pounds per 3,000 square feet,and then dried. The yellow coating composition of example 2 is applied,as by silk screen in a coating weight of about 15 pounds per 3,000square feet of surface area in a pattern of closely spaced parallellines 22 which extend crosswise over the surface of the first coating20. lt will be understood that the described coatings can be applied invarious other sequences such as a first coating of the yellow coat ofexample 2 followed by second and third coatings of example I and 3, or afirst coat of example 3 and second and third coatings of examples 3 and2 or 2 and 3, etc.

The cyan coating composition of example 3 is also applied, as by silkscreen in a coating weight of about 15 pounds per 3,000 square feet ofsurface area in a pattern of closely parallel lines 24 which extendlengthwise over the first and second coatings to provide crossoverpoints 26 having three thicknesses of coating with the third coating 24uppermost on the face of the substrate or paper base sheet.

The final coated sheet constitutes a receptor suitable for use in thepractice of this invention with separate sections 28 having asingle-coating thickness of the magenta coating, separate sections 30having a double-coating thickness formed of a lowermost magenta coating20 and an uppermost yellow coating 22 and a lowermost magenta coating 20and an uppermost cyan coating 24 and still other sections 32 having atriple coating thickness formed of a lowermost magenta coating 20, anintermediate yellow coating 22 and an uppermost cyan coating 24. Thusthe exposed face of the receptor presents separate sections of each ofthe coatings in substantially uniformly dispersed relation over the faceof the receptor sheet.

The receptor sheet is charged in the usual manner, now well known to theelectrostatic copy art, as by subjecting the face of the receptor to acorona spray as it is exposed to corona discharge from wires operatingat a potential of about 6,000 to 8,000 volts. The charged wires, whichextend across the face of the receptor, are either transported over theface of the receptor or the receptor is displaced beneath the wires. Theelectrostatic charge is deposited over the entire receptor covered byone or more of the photoconductive coatings.

The charged receptor is next exposed to the multicolor original. Suchportions of the original which are blue in color, for example, willcause discharge of the corresponding areas on the face of the receptorformed of the yellow coating which is sensitized to blue, leaving thecharges in the corresponding areas on the exposed face sections of themagenta and cyan coatings for subsequent development.

The portions of the original which are green in color cause discharge ofthe corresponding areas 28 on the face of the receptor of the magentacoating, which are sensitized to green, leaving the charge 34 on thecorresponding areas on the face sections 32 of cyan and sections 30 ofthe yellow coating for subsequent development, as depicted in H6. 3.

Similarly, the portions of the original which have the color red willcause discharge in the corresponding areas of the receptor of the cyansections'32 on the exposed face of the receptor sheet which aresensitized to red, leaving the charges on the corresponding areas in theexposed faces sections of magenta and yellow for subsequent development.

The exposed receptor sheet is developed in the conventional mannereither with a dry powder developer or with a liquid developer, but inwhich the conventional particles of toner in the dry powder developersuspended in the liquid developer are substituted by finely dividedparticles of a compound which, when activated as by heat or solvent,vapor and the like, becomes a solvent for the dispersed dye in thecoating.

The following examples are given by way of illustration, but not by wayof limitation, of liquid developing compositions embodying the featuresof this invention:

EXAMPLE 4 5.0 grams toner (Antipyrine) 400 ml. liquid carrier (lsoparG-Humble Oil Co.) 5 grams charge director (Fuel Oil Additive No.2--DuPont EXAMPLE 5 5.0 grams toner (l-allyl-Z-thiourea) 400 ml. liquidcarrier 5 grams charge director The Isopar G used as the liquid carrierin the above example is parafi'mic hydrocarbon liquid having 1l.8percent C hydrocarbons, 56.2 percent C hydrocarbons, 31.7 percent Chydrocarbons, less than 0.3 aromatics and less than 0.1 olefins, aboiling point within the range of 3l8-350 F., a flash point of 104 F.and a specific gravity of 0.748. Other liquid carriers used in liquiddevelopers may be used as long as the toner compound is not dissolvedtherein. The Fuel Oil Additive No. 2 is a solution of a methacrylatecopolymer having an average molecular weight of 50,000. Again, otherconventional charge directors can be employed.

The antipyrine of example 4 and the l-allyl-Z-thiourea of example 5 aremerely representative of suitable toner particles which may be used fordevelopment of the latent electrostatic image of the charged sectionsthat remain after exposure. Other toner particles may be used which meetthe requirements:

1. a solvent for the soluble dye component in the coatings when thetoner is in a molten or activated state;

2. capable of being reduced to a finely divided form in which it isretained in the liquid or powdered developer composition;

3. capable of taking on a charge, such as a positive charge when usedwith a charged photoconductive coating of zinc oxide;

. suitably located within the triboelectric series to produce thedesirable charge development. Representative of other suitable compoundswhich meet these requirements and can be used as toners are vanillin,1,6-hexanediol, 1,10decanediol, ethyl urea, acetamide, benzohydrol, 2,2-dimethyl-l,3-propanediol, ammonium acetate, ammonium formate andpyrazine. The toner particles can be employed in various concentrationsin the developer composition, such as within the range of 2-20 percentby weight, and preferably 3-10 percent by weight, in a dry powderdeveloper and within the range of 02-20 percent by weight and preferably2-10 percent by weight in a liquid developer. When use is made of a drypowdered developer which is applied by brushing or the like, the tonerconcentration can range up to 100 percent by weight toner in thedeveloper.

Continuing with the development process, in response to the applicationof the developer composition, toner particles 36 will be retained theportions of the face of the receptor which remain charged to define thelatent electrostatic image after exposure while the discharge sectionson the face of the receptor will remain substantially free of the tonerparticles, as depicted in FIG. 41.

Thereafter the developer receptor sheet is pressed into surface contactwith a copy sheet 40, as by passage of the composite assembly betweencompression rollers heated to a temperature above the melting pointtemperature for the toner, such as at a temperature above lll-l 13 C.which is the melting point for antipyrine, or above a temperature of77-78 C. which is the melting point for l-allyl-2-thiourea, andpreferably by heating the toner particles to a temperature which exceedstheir melting point by a slight amount preferably about 5-l0 lF. As aresult, the toner particles are reduced to a fluidized state to enablesolution of the dispersed dye in the underlying portions of thephotoconductive coating in the face of the receptor for transfer of thecorresponding dye color, as by diffusion, from the receptor to the copysheet 40.

1n the example illustrated in FIGS. 4 and 5, the cyan and yellowcoatings 32 and 30, respectively, which remain charged and retain thetoner particles 34 on development, solubilize the Calcofast SpiritYellow TG and the Spirit Soluble Fast Blue 6G to cause transfer to thecopy sheet with the resultant reproductions 50 of the green color of theoriginal. In such areas of the original which are black, such as theprinted areas, none of the sections in the face of the coated receptorwould become discharged upon exposure. As a result, each of the areasaccept toner for transfer of dyestuffs from all of the three basic colorsections which together appear black in the copy sheet.

It will be apparent that the copy produced by the combination of colorstransferred from the developed receptor sheet will correspond to thecolored original and that the developed receptor can function in amanner of a spirit master to produce multiple copies of the multicolororiginal, as by the successive passage of copy sheets into pressurecontact with the developed receptor until the soluble dyestuff in thetoned face segments are exhausted.

It will be apparent from the foregoing that I have provided a new andnovel electrophotographic process for the production of true colorcopies of multicolor originals by the use of but a single exposure forthe development of a master from which one or more multicolor copies canbe produced.

It will be understood that changes may be made in the details offormulation, application and process steps without departing from thespirit of the invention, especially as defined in the following claims.

We claim:

1. An electrophotographic process for the production of multicolorcopies of a multicolor original comprising the steps of applying anelectrostatic charge onto the face of a receptor formed of a substratehaving on its face interspersed sections of two or more photoconductivecoatings each of which contains a photoconductive component, asensitizer for the photoconductive component and a solubilizable dye, inwhich the sensitizer in one coating sensitizes the photoconductor to aparticular segment of the visible light range for absorption of lightwithin said range and reflection of light outside said range, and inwhich the solubilizable dye corresponds with the color of the reflectedlight, and in which separate coatings are provided with sensitizingcomponents designed to cover substantially the entire visible lightrange, whereby and electrostatic charge is retained by each of saidphotoconductive coatings, exposing the charge receptor to the originalwhereby the sections on the face of the receptor are discharged inresponse to exposure to color in corresponding areas of the original towhich the particular sections have been sensitized, leaving the chargeon the sections from which the light has been reflected, developing theexposed receptor with a developer containing a toner in the form offinely divided particles of a material which is a solvent for thedyestuff in response to activation whereby toner is retained on thesections retaining the electrostatic charge, ans bringing a copy sheetin surface contact with the face of the developed receptor with thetoner in an activated stage to cause transfer of solubilized dye colorsfrom the corresponding areas of the receptor to the copy sheet.

2. The process as claimed in claim 1 in which the interspersed sectionsof photoconductive coatings comprise interspersed sections of threeseparate coating systems sensitized to the additive primary colors ofred, green, blue, respectively.

3. The process as claimed in claim 1 in which the photoconductorcomponent of the photoconductive coating comprises photoconductive zincoxide.

4. The process as claimed in claim 1 in which the sensitizing componentis a sensitizing dye.

5. The process as claimed in claim 4 in which the sensitizing dye idpresent in the coating in an amount within the range of 0.001 to 5.0percent by weight when the photoconductive component is aphotoconductive zinc oxide with the said percentage varying inproportion to the weight of zinc oxide and other photoconductor whensaid other photoconductor forms the photoconductive component.

9. The process as claimed in claim 1 in which the toner is an organiccompound selected from the group consisting of antipyrene and1-allyl-2-thiourea 10. The process as claimed in claim 1 in which thetoner has a melting point at a temperature above ambient temperature andin which activation of the toner comprises the step of heating thecoated receptor to a temperature above the melting point temperature ofthe toner while the copy sheet is in pressure contact with the face ofthe receptor.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,630,729 DatedDecember 28, 1971 Frederick O. Bach et al.

Patent No.

Inventor(s) It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

column 1, line 43, after "sensitizing" cancal "wavelength within" andsubstitute dye which sensitizes column 2, after line 55, insert thefollowing line:

"specified in parts by weight may be taken as corresponding";

column 6, line 44, change "and" to "an" (SEAL) Attest:

EDWARD TLFLETGI-IFH JR ROBERT GOT TSCHALK Attesting Officer ICommissioner of Patents USCOMM-DC 60376-P69 us. GOVERNMENT PRINTINGornc: I969 0-365-334 FORM PO-105O (10-69)

2. The process as claimed in claim 1 in which the interspersed sectionsof photoconductive coatings comprise interspersed sections of threeseparate coating systems sensitized to the additive primary colors ofred, green, blue, respectively.
 3. The process as claimed in claim 1 inwhich the photoconductor component of the photoconductive coatingcomprises photoconductive zinc oxide.
 4. The process as claimed in claim1 in which the sensitizing component is a sensitizing dye.
 5. Theprocess as claimed in claim 4 in which the sensitizing dye id present inthe coating in an amount within the range of 0.001 to 5.0 percent byweight when the photoconductive component is a photoconductive zincoxide with the said percentage varying in proportion to the weight ofzinc oxide and other photoconductor when said other photoconductor formsthe photoconductive component.
 6. The process as claimed in claim 1 inwhich the colored dye component corresponding to reflected light is adispersed dye.
 7. The process as claimed in claim 6 in which thedispersed dye is a spirit soluble dye.
 8. The process as claimed inclaim 6 in which the dye component is present in an amount within therange of 0.5 to 20 parts by weight per 100 parts by weight of thephotoconductive component when that photoconductive component is zincoxide.
 9. The process as claimed in claim 1 in which the toner is anorganic compound selected from the group consisting of antipyrene and1-allyl-2-thiourea
 10. The process as claimed in claim 1 in which thetoner has a melting point at a temperature above ambient temperature andin which activation of the toner comprises the step of heating thecoated receptor to a temperature above the melting point temperature ofthe toner while the copy sheet is in pressure contact with the face ofthe receptor.